When endless joining is applied to a conveyer belt, in the practice of the ordinary art, it is necessary to strip off all the steel cords embedded in the conveyer belt at both terminals of the conveyer belt with a predetermined length.
Conventionally, under cover rubber and upper cover rubber of the belt that is clamped at a predetermined place are manually removed by using a knife. Thereafter, bonding rubber portions positioned between each steel cords are vertically cut by using a knife or the electric heating cutter disclosed in Japanese Patent Application Publication (JP-B) No. 46-39614, and then the bonding rubber portion around each steel cords are cut off by using a knife.
As each operation in the above-mentioned three steps has been manually carried out using existing tools in conventional art, therefore, operation efficiency could not be achieved. For example, the work man-hour of 8 people×16 hours is required to strip all the steel cords off from the conveyer belt by using knives, where the width of the belt is 1,800 mm, the embedded steel cords are 11.0 mm (diameter)×110 (number), and thickness of cover rubber is 16 mm×8 mm.
Moreover, the cutting operation of rubber using knives is a hard labor and causes considerable fatigues. Furthermore, only skilled workers can successfully carry out the cutting operation of rubber by using knives. Since it is extremely difficult to remove rubber portions completely and uniformly from entire length of steel cords, as mentioned above, irregularity of the rubber portion is remained around steel cords in practices. Consequently, problems arise in that numerous man-hour is also required in a modifying operation during a molding step, which is performed later.
There is also a problem in that either repeated grinding of blade or replacement of blade is required and surface strands of steel cords are easily damaged, all because the blade edge has extensive contacts with steel cords during the cutting operation of rubber portion.
In the case of performing the cutting operation of rubber portion using the electric heating cutter disclosed JP-B No. 46-39614 in which the blade having U-shape in elevation is disposed, cutting resistance causes deformation of the heated U-shaped blade, and this deformation and the like lead to failure in cutting a bonding rubber portion at a very early stage.
In order to overcome the above-mentioned problems, inventors of the present invention suggest, as shown in FIGS. 14A to 14C, the apparatus for cutting a rubber portion of conveyer belt “40” disposing a cylindrical blade part “41” and straight blade parts “42”, in JP-A 63-267193. In the apparatus, the straight blade parts “42”, “42” are disposed both ends of the cylindrical blade part 41 so as to have the straight blade parts “42”, “42” protrude from the cylindrical blade part “41”, and the cylindrical blade part “41” is configured to surround a steel cord embedded in a conveyer belt.
This suggested apparatus realizes a cutting operation, which cut off rubber portions completely and uniformly from a predetermined length of steel cords, without any skills and with only a little man-hour. Moreover, the apparatus enables to prevent damages on surface strands of the steel cords.
However, the apparatus disclosed in JP-A 63-267193 still has problems to be solved. To be specific, the cylindrical blade part “41”, the straight blade parts “42”, “42”, and brackets “43a”, “43b” are disposed forming an integral construction (including an integration by rivets). When only one of the cylindrical blade part and the straight blade parts has impaired sharpness or is damaged, therefore, the whole integral construction is required to be replaced. Generally, the straight blade parts needs to be grinded more frequently compared with the cylindrical blade part. As a consequence, it is inefficient in its operation and cost.
Additionally, cutting resistance becomes large because of the integral construction of the cylindrical blade part “41” and the straight blade part “42” as shown in FIGS. 14A to 14C. Especially in the case that thick, high strength steel cords having a diameter of 9 mm to 13 mm, which are embedded in a conveyer belt, the blade edge of the cylindrical blade prone to lean towards traveling direction thereof. This leads the blade edge to contact with a steel cord, hence, the steel cord may be damaged.
Further, the apparatus for cutting a rubber portion “40” does not accommodate a member for controlling twist (curvature) of the conveyer belt, which is to be cut, by drawbar pull during cutting, therefore the blades receive extra cutting resistance and this results in rapid wear of blades. As a double blade of cutting blades and bracket parts “43a” and “43b” is secured only by rivets, moreover, edge of the cylindrical blade part “41” is widen by drawbar pull when cutting. Consequently, there is a problem in that diameters of the cut cylindrical steel cords vary.
Under these circumstances, the present invention aims at solving conventional problems and achieving following tasks.
Namely, it is an object of the present invention to provide an apparatus and method for cutting a rubber portion of conveyer belt, which are suitable for cutting a rubber portion positioned between each steel cords embedded therein so as to separate each steel cords, and cut off the rubber portion completely and uniformly from each steel cords at predetermined length.